Reflector bulb lamp



Nqv. 28, 1939.

. o. H. BIGGS 2.181392 REFLECTOR'BULB LAMP Filed NOV. 2, 1937 lnyemfor':

- Attorney,

Patented Nov. 28,

UNITED STATES PATENT ornea 2,181,292 REFLECTOR BU B LAMP Orrlck n.Biggs, Beverly, Masa, assignor to Hygrade Sylvania Corporation, Salem,Mesa, a, corporation of Massachusetts Application November 2, 1937,Serial No. 112,397

2 Claims. (01. 176-34) The object of this invention is to provide anelectric lamp which produces a directed beam of light, and in particularto provide an electric incandescent lamp with a reflecting coating onits bulb and a filament positioned within the reflector to give adirected beam of light.

A further object of the invention is to provide an electric incandescentlamp with a bulb having a bowl portion and a skirt portion, a reflectorcoating over the interior of the skirt portion, and an incandescentfilament set close to the narrow end of the skirt portion to give adirected beam of light through the bowl portion.

Still another object is to provide, for such a lamp, a reflecting layerwhich is protected by a transparent protective coating which also actsas a getter to increase the useful life of the lamp.

Other objects are to provide a reflecting shield between the filamentand the neck of the bulb,- to insure the utilization of light otherwiselost in the neck.

Further objects and advantages of the invention will be evident from thefollowing description, taken in connection with the accompanyingdrawing, in which:

Figure 1 is a side view, partly in section, of a lamp according to theinvention;

Figure 2 is a schematic view of the light from a filament placed in aplane perpendicular to the longitudinal axis of the reflector; and

Figure 3 is a schematic view of the light from a filament placedparallel to, or along the longitudinal axis of the reflector.

While the invention may take various forms a preferred embodiment isshown in Figure 1. With reference to the figure, the lamp bulb containsa bowl portion 2, which may be transparent or translucent, and may becolored, if desired; a skirt portion 3, the interior surface of whichcarries a layer 4 of reflecting material, such as a metal or an enamel,and which may, if desired, be covered by a thin transparent protectivecoating 5. The filament 6 is disposed near the narrow portion of thebulb, near the neck I, rather than in its usual position near the centerof the bulb, in order to give a narrow light beam. A shield 8 ofreflecting material is placed in back of and near the filament, asshown, and may be supported from the leads I, I. The reflecting surfaceof the shield may be covered with a protective coating if desired. Toreduce evaporation of the filament during Operation, an atmosphere ofinert gas such as nitrogen, argon or krypton, the latter two beingbetter, and preferably at a pressure above half an atmosphere is usedinside the bulb.

Any form of contact base 9 may be attached to the lamp.

If desired, the filament may be arranged in a plane perpendicular to thelongitudinal axis of the reflecton; In this case, nearly 50%-of thelight emitted by the filament is in the backward direction, denotedroughly by the arrow II, in Figure 2, and would be lost in the neck I ofthe bulb, if the reflecting shield 8 were not placed behind, and closeto the filament. The light in backward directions, such as thatschematically shown by arrow I I, is thus reflected by the shield, whilethe light coming from the front of the fila- -ment will either emergedirectly from the lamp or be reflected from the layer 4 as shown byarrow l2, which depicts the path of. a ray of light from filament 6 inFigure 2.

The shield, in such a position, is subjected to the heat absorbed fromthe filament radiation, and if the lamp is used base up, to the heatcarried by convection of the hot gases of the lamp filling. It is thuspreferably made of aluminum, which remains bright after subjection tohigh temperatures, and may be supported from the leads of the filament,but must, of course, ifof metal, be insulated from at least one of theleads to prevent short-circuiting them.

With the filament placed as in the preceding paragraph, nearly 50% ofthe light has to be reflected from the small shield 8. If, however, thefilament is placed parallel to, or along the longitudinal axis of thereflector, as in Figure 3, the small shield 8 is not required to controlas large a proportion of the total light or radiation, and may runcooler, thus avoiding damaging its reflecting power. In this case, thelight emitted from both sides of the filament is reflected. by the layer4, as shown by the arrows in Figure 3. The light in the directionpf thearrow I l is nearly zero, since the only part of the filament visible inthat direction is about the diameter of the coil. The light in thebackward direction is thus nearly zero along arrow H, and small in thegeneral backward direction, so that shield 8 is required to control onlya small part of the total emitted light. The shield 8, is preferablycurved slightly, or slightly V-shaped as shown in Figure 1, so thatlight hitting it from the filament will be reflected directly out of thebulb through the clear portion 2.

The reflecting" layer 4 may be of a highly refleeting enamel or thelike, either white or colored as desired, or may be of metal, depositedby the well-known chemical processes or by the evaporation processdescribed in copending application Serial No. 691,322, filed September28, 1933. Silver may be used, if desired, but aluminum will generally bebetter, because it will retain its brightness better after going throughthe usual lamp manufacturing processes. The aluminum may be oxidizedslightly, either chemically or electrolytically, to form a thintransparent protective coating over its surface. This coating, if formedbefore the manufacturing processes, will enable the aluminum towithstand the severe heat treatment found beneficial to the lamp duringmanufacture.

The reflecting layer preferably extends from the neck I of the bulb tothe point in of largest diameter of the bulb, but generally not beyond,since any reflector on the bowl surface of the bulb would reflect lightin the backward direction, and reduce the emciency of the lamp.

This application is in part a continuation of application Serial Nos.691,322 and 114,562, filed, respectively, September 28, 1933, andDecember 7, 1936. Application Serial No. 691,322 was issued July 12,1938 as United States Patent No. 2,123,706. It will often be desirable,in order to have a mole concentrated and straight filament forrefiection purposes, to use a so-called coiled-coil ordoubly-coiledfilament, as shown for example in U. S. Patent 2,067,746, issued January12, 1937, to R. M. Zabel.

The beam from a reflector lamp as shown will generally be narrower whenthe conical skirt is long and narrow, that is when the angle of the coneis small. It may often be desirable to have a cone angle of say 45 nearthe filament, as shown in Figure 3, and a cone of much narrower angle ata distance from the filament. The skirt may, of course, be a paraboloidof revolution, if desired, particularly if the filament is soconcentrated as to be almost a point source.

What I claim is:

1. In an incandescent lamp, a sealed glass bulb having a bowl portionand a conical skirt portion, a reflecting coating of aluminum on theinterior surface of said skirt portion, a thin transparent protectiveoxide coating over said aluminum coating, a filament of doubly coiledtungsten wire set inside the narrow end of said skirt portion and withits longitudinal axis along the longitudinal axis of the lamp, aV-shaped aluminum shield set behind said filament and supported by theleads to said filament, being insulated from at least one of. saidleads, the open end of the V facing toward the bowl portion of the lamp,and a filling of argon at greater than half an atmosphere pressure inthe bulb.

2'. In an incandescent lamp, a sealed glass bulb having a bowl portionand a frusto-conical skirt portion, a metallic reflecting coating on theinterior surface of said frusto-conical skirt portion, a filament coilof diameter small compared to its length set inside the narrow end ofthe conical skirt and parallel to the longitudinal axis of said skirt tocooperate with the reflecting coating to direct a beam of reflectedlight through the bowl portion of the bulb, and a filling of inert gaswithin said bulb.

ORRICK H. BIGGS.

